This invention relates to a new and useful apparatus for determining the swing inertia of golf clubs.
Golf clubs manufacturers have arrived at a method of what they term a balance of the clubs in order that all the clubs in a set supposedly can be matched for swing feel. Such is known as the "swing weight" of the clubs and as stated is intended to give the golfer the same swing feel of all clubs in the set. Such swing weight is not a determination of the center of gravity of a club but appears only to be an assumed location on the club of a point for calibrating a uniform feel of all the clubs in a set.
A beam scale is used having a slidable weight which can be adjusted relative to calibrations reading in letters and divisions thereof, such as D1, D2, etc. The butt end of the club is set against a stop on the scale approximately 14 inches from the beam pivot. A two iron is usually about 39 inches long and clubs with more loft reduce in length in approximately one-half inch increments through the nine iron and wedge. When a two iron is placed on the scale, approximately 25 inches extend beyond the scale's pivot point toward the club head. As the progressively shorter clubs are gauged on the scale, the heads obviously must increase in weight to maintain the same balance position of the sliding weight and the scale reading. It is customary to add or delete weight from the butt end of the club to achieve the desired swing weight balance of the club.
The above method and apparatus for determining the swing weight of clubs have the disadvantage that the ratio of the distances between the beam pivot of the scale and the butt end of the club and the pivot and the club head end requires rapid and excessive increase of weight to maintain the balance, with the result that when a golfer swings a two iron for example it will feel lighter than when he or she swings a nine iron. This of course destroys the present intention of swing weight because such intention is to obtain an identical swing feel for all clubs. Obviously, such feel is not present.
Another disadvantage of the presently used method and apparatus for changing the swing weight of clubs is that when weight is added to the butt end of the clubs to bring the swing weight down, the club will obviously increase in overall weight. Thus, if a golfer wants to reduce the swing weight of his or her clubs, weights are placed in the butt end of the clubs. While this may provide a balance on the scales presently used to reduce the swing weight of the club, the actual weight of the club is increased. If a person desires a reduced swing weight, it follows that the person also desires a club of lighter over-all weight, and this increased weight of the clubs may be extremely disadvantageous to persons who do not want a heavier club.
According to the present invention and forming objectives thereof, apparatus is provided for establishing a swing feel for golf clubs that is concerned with the pivot position of the clubs relative to the inertial resistance to wrist and hand torque applied to the clubs rather than with an arbitrary point of balance which exists on the shaft forward of the grip of the club. The present apparatus provides a means for precisely matching all the clubs in a set for the same feel and for coordinating what is termed herein as the swing inertia with the overall weight of the club, as well as a means which appears to be more logical when considering that the feel of the club is related to torque applied through the hands and wrists.
In carrying out the objectives of the invention, the method of the apparatus comprises the steps of using a calibrated set of values of swing inertia and gaging the clubs in a set on a gravitational scale provided with the said calibrations. The clubs are counterbalanced at the axis of rotation of a person's normal grip on the grip portion for swinging the club, and each club is adjusted to a similar swing inertia calibration by varying the weight of the head of the club. The calibrations comprise the length of the club shaft from the scale pivot point to the center of gravity of the club head multiplied by the head weight of the club. To accomplish this method of determining the swing inertia of clubs, a gravitational scale includes a balance beam with support means for supporting a golf club in parallel relation therewith. The beam supports the club thereon with the point comprising the axis of rotation of a person's hands as gripped on the grip portion of the club disposed vertically above the pivot point of the beam. Calibrations on the scale comprise the length of the golf club from the scale pivot point to the center of gravity of the head multiplied by the head weight of the club. The support for the club is adjustable for positioning different length clubs with the axis of rotation of the hands disposed vertically above the pivot point of the beam. The scale also includes means for determining the over-all weight of the clubs.
The invention will be better understood and additional objects and advantages will become apparent from the following description taken in connection with the accompanying drawings.